Urease, distribution

An enzyme deposited on the LAPS surface allows one to observe the spatial distribution of a specific substrate. In a urea-selective sensor urease was immobilized on a pH-selective LAPS [75],... 

The diagnosis of HP infection can be made using endoscopic or nonendoscopic tests (Table 33-6). The tests that require upper endoscopy are more expensive, uncomfortable, and require a mucosal biopsy for histology, culture, or detection of urease activity. Recommendations to maximize the diagnostic yield include taking at least three tissue samples from specific areas of the stomach, as patchy distribution of HP infection can lead to false-negative results. Because certain medications may decrease the sensitivity of these tests, antibiotics and bismuth salts should be withheld for 4 weeks and PPIs for 1 to 2 weeks prior to endoscopic testing. 

CaCO, Microspherulites Containing Enzymes were prepared as in Ref [6]. One volume of a 1M CaCl aqueous solution was added to two volumes of enzyme solution (1.0 mg/mL) with vigorous stirring. Then an equal volume of aqueous 0.33 M Na COj was rapidly added. After stirring for 30 s, the suspension of particles was allowed to stand for 15 min at room temperature without stirring. The formation of microspheruhtes was controlled with a light microscope. These composite micro-sphemlites with inclusions of urease or LDH had a narrow size distribution with a mean diameter of 4.5 pm. 

Chemical sensing and biosensing were performed using an ammonium-selective PVC-membrane and a urease-membrane, additionally [4] Both membranes were successively coated onto the sensor array The membranes were completely covered with pure buffer solution, whereas the double liquid lunction was filled with 1 0 M ammonium chloride or urea in the same buffer solution Thus, after the contact of the double liquid junction and the buffer solution on the chip ammonium chloride or urea, respectively, diffused into the pure buffer solution on the chip, finally resulting in a homogeneous distribution all over the sensor array The distribution of ammonium chloride as well as urea was imaged by successive scans in potentiometric mode The scan time for a complete potentiometric scan was alwavs 2 5 min... 

Urease catalyzes the hydrolysis of urea to yield carbon dioxide and ammonia. Urease activity is common in higher plants, bacteria, and molds but is of limited distribution in animals. In no case has ureolytic activity been reported in the liver of vertebrates, although urea may be hydrolyzed by gastric mucosa and erythrocytes. Since urease was the first enzyme to be isolated in crystalline form, it has been the object of considerable study. 

Urease, the enzyme responsible for the alkaline fermentation of urine, is widely distributed through the vegetable kingdom. 

Decomposition by Urease.— Urea is rapidly and completely converted into ammonia and carbon dioxide by the widely distributed enzyme urease which is found in the seeds of many l uminous plants and in many micro-organisms. The chief sources of mease... 

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